Cement-manufacturing plant and process for producing cement clinker

ABSTRACT

A cement production plant may include a preheater for preheating raw meal, a calciner for calcining the preheated raw meal, and a furnace with a furnace burner for firing the raw meal to form cement clinker. The furnace has a combustion gas inlet for admitting a combustion gas with an oxygen content of 30% to 75% into the furnace. The cement production plant may also include a cooler for cooling the cement clinker. The calciner and the furnace each have at least one respective fuel inlet for admitting at least one fuel into the calciner and the furnace. The calciner and the furnace each have at least one respective inert gas inlet for respectively admitting inert gas into the calciner and the furnace.

The invention relates to a cement production plant and a method forproducing cement clinker, wherein inert gas is introduced into at leastone combustion process.

It is known from the prior art to feed oxygen-containing gas for thecombustion of carbonaceous fuel into the rotary furnace or the calcinerof a cement production plant. In order to reduce the amount of exhaustgas and to be able to dispense with complex purification processes, itis known, for example, from DE 10 2018 206 673 A1 to use a combustiongas that is as rich in oxygen as possible so that the CO2 content in theexhaust gas is high, Document DE 10 2018 206 673 A1 discloses theintroduction of an oxygen-rich gas into the cooler inlet region forpreheating the gas and cooling the clinker.

When using oxygen-enriched combustion gases that have a high oxygencontent of at least 30% to 100%, very high temperatures can occur in thecalciner and the furnace. If these high temperatures occur for a longerperiod of time or permanently in the region near the wall of thecalciner, this can result in damage to the inner wall of the calciner.When hot zones occur in combination with the hot meal introduced,melting phases of the hot meal to be calcined are also to be expected.Based on this, it is the object of the present invention to provide acement production plant and a method for producing cement, wherein asafe operation of the furnace line is ensured and at the same time anexhaust gas with a high CO2 content is obtained. An extended object isto charge the preheated raw meal into the calciner in an evenlydistributed manner and to bring it into interaction with the hot gasesproduced as a result of the calciner firing. A preferred object of theinvention is to realize the calciner firing by the targeted introductionof fuels, oxygen-containing gases, and hot raw meal in a staged form, sothat a complete conversion of the introduced fuels, a completecalcination of the introduced raw meal particles, and the transport ofthe solid particles along the riser of the calciner are ensured withoutoverheating in the riser and agglomeration of the solid particles alongthe riser.

In accordance with the invention, this object is achieved by a cementproduction plant having the features of independent Device claim 1 andby a method having the features of independent Method claim 12.Advantageous developments can be found in the dependent claims.

According to one aspect of the invention, a cement production plantcomprises:

-   -   a preheater for preheating raw meal,    -   a calciner for calcining the preheated raw meal,    -   a furnace with a furnace burner, such as a burner lance, for        firing the calcined hot meal to form cement clinker, wherein the        furnace has a combustion gas inlet for admitting a combustion        gas with an oxygen content of 30% to 100% into the furnace, and    -   a cooler for cooling the cement clinker, 1

wherein the calciner and the furnace each have at least one respectivefuel inlet for admitting fuel into the calciner and into the furnace.

The calciner and the furnace each have at least one respective inert gasinlet for respectively admitting inert gas into the calciner and thefurnace.

The preheater of the cement production plant preferably comprises aplurality of cyclone stages, each with at least one cyclone forseparating solids from the gas flow. The invention makes it possible tooperate the preheater with a significantly lower gas volume compared toa cement production plant that uses air as combustion gas. For example,the exhaust gas volume flow after the preheater is about 0.50 to 0.90Nm3/kg clinker. The ratio of the feed quantity of raw meal to exhaustgas is accordingly higher possibly than in plants that are operated withair and is, for example, up to 3 kg/kg solids to gas, preferably 1.3 to1.9 kg/kg solids to gas. In the preheater, the raw meal fed to theuppermost, first cyclone stage is preheated in counterflow to thefurnace exhaust gases and passes here through the cyclone stages oneafter the other.

Between the last and the penultimate cyclone stage, the calciner isarranged, which has a riser into which the raw meal is heated by meansof a calciner firing, which may consist of one or more firing positions.The calciner preferably comprises a fuel charging apparatus comprisingthe fuel inlet and the inert gas inlet. The fuel charging apparatus isfor example tubular or formed as a radial bulge on the riser pipe of thecalciner, Preferably, the fuel charging apparatus opens out into theriser pipe of the calciner so that fuel and/or inert gas are fed intothe riser pipe of the calciner via the fuel charging apparatus. The fuelcharging apparatus is a thermal treatment chamber that is used forheating and controlled addition of fuel into the riser.

Advantageously, the solids-to-gas ratio in the calciner is significantlyhigher compared to conventional systems with air as the oxidizer. Forexample, solids loadings of more than 2 kg per kg of gas occur locally,for example 2 to 8 kg per kg of gas. In the calciner, preferably thelargest part, more than 60%, for example about 80%, of the fuel heat isconverted. Due to the raw meal introduced at the lower end of thecalciner, despite an initial oxygen concentration of 40-80%, whichinitiates intensive firing, there is a sufficient heat sink to preventoverheating. If lumpy substitute fuel, for example with edge lengthsof >100 mm, is to be burned, an inclined region with a higher residencetime for the fuel should preferably be provided. Examples of suchinclined regions are stair treads, push grates, push-back grates orother mechanical or pneumatic devices. These devices function, forexample, as combustion chambers, pre-combustion chambers or serve onlyfor drying and preheating or partial gasification of the introducedfuels. The fuels can be of any type with regard to their particle sizedistribution and calorific value.

For example, the calcination reaction takes place under CO2 partialpressures between 10%-60% at the beginning of the calciner and up to 98%at the end of the calciner. Accordingly, the calcination reactionpreferably proceeds at higher temperatures of 700 to 1100° C.,preferably 900-1000° C., than in the conventional plant.

The raw meal preheated in the preheater and calcined in the calciner isthen fed to the furnace. The furnace is preferably a rotary furnace witha rotary tube that can be rotated about its longitudinal axis and ispreferably slightly inclined in the direction of conveyance of thematerial to be fired, so that the material is moved in the direction ofconveyance due to the rotation of the rotary tube and gravity. Thefurnace preferably has a material inlet at one end thereof for admittingpreheated, calcined raw meal and a material outlet at its end oppositethe material inlet for discharging the fired clinker into the cooler. Atthe end of the furnace on the material outlet side, there is preferablya furnace head comprising the furnace burner for firing the material andpreferably at least one fuel inlet for admitting fuel into the furnace,preferably via a furnace burner and/or via a fuel lance. The furnacepreferably comprises a sintering zone in which the material is at leastpartially melted and in particular has a temperature of 1500° C. to1900° C., preferably 1450° C. to 1750° C. The sintering zone comprises,for example, the furnace head, preferably the rear third of the furnacein the direction of conveyance of the material.

For example, all or part of the oxygen-containing combustion gas isintroduced directly into the furnace head, wherein the furnace head has,for example, a combustion gas inlet. Preferably, the combustion gas isfully or partially introduced into the furnace via the material outletof the furnace. The combustion gas supplied to the furnace has, forexample, an oxygen content of more than 30% to 75%, preferably more than95%. For example, the combustion gas consists entirely of pure oxygen,wherein in this case the oxygen content of the combustion gas is 100%.The furnace burner may be, for example, a burner lance. The cooler forcooling the cement clinker is preferably connected to the materialoutlet of the furnace.

The cooler has a conveying device for conveying the bulk material in thedirection of conveyance through the cooling gas chamber. The cooling gaschamber comprises a first cooling gas chamber portion with a firstcooling gas flow and, adjoining this in the direction of conveyance ofthe bulk material, a second cooling gas chamber portion with a secondcooling gas flow. The cooling gas chamber is preferably bounded at thetop by a cooling gas chamber ceiling and at the bottom by a dynamicand/or static grate, preferably by the bulk material lying thereon. Thecooling gas chamber is in particular the entire chamber of the coolerabove the bulk material through which cooling gas flows. The cooling gasflow passes through the dynamic and/or static grate, in particularthrough the conveying device, through the bulk material and into thecooling gas chamber. The first cooling gas chamber portion is preferablyarranged, in the direction of flow of the bulk material to be cooled,directly after the cooler inlet, in particular the material outlet ofthe furnace. Preferably, the clinker falls out of the furnace into thefirst cooling gas chamber portion.

The first cooling chamber portion preferably has a static grate and/ordynamic grate arranged below the material outlet of the furnace so thatthe clinker exiting the furnace falls onto the static grate due togravity. Preferably, only the first cooling gas flow flows into thefirst cooling gas chamber portion and is accelerated, for example, bymeans of a fan or pressure-loaded boiler or corresponding other device.The second cooling gas chamber portion adjoins the first cooling gaschamber portion in the direction of conveyance of the bulk material andis preferably separated from the first cooling gas chamber portion interms of gas by means of a separating device. Preferably, only thesecond cooling gas flow, which is accelerated by means of at least onefan, flows into the second cooling gas chamber portion.

The second cooling gas chamber portion preferably has a dynamic gratefor conveying the bulk material through the cooling gas chamber. Thefirst cooling gas flow flowing through the first cooling gas chamberportion is, for example, pure oxygen or a gas with a content of lessthan 35 vol %. in particular less than 21 vol %, preferably 15 vol % orless of nitrogen and/or argon and/or with an oxygen content of more than20.5%, in particular more than 30% to 75%, preferably more than 95%. Thefirst cooling gas chamber portion preferably connects directly to thematerial outlet of the furnace, preferably to the furnace head of thefurnace, so that the cooling gas is heated in the cooler andsubsequently flows into the rotary furnace and is used as combustiongas. The second cooling gas flow is, for example, air.

The cooler preferably has a separating device for separating the coolinggas chamber portions from each other in terms of gas.

The inert gas is for example CO2 or water vapour. The introduction ofinert gas into the calciner and/or the furnace offers the advantage ofdelaying, in particular slowing down, the combustion so that damage tothe furnace and/or the calciner is prevented.

According to a first embodiment, the fuel inlet and the inert gas inletare arranged separately from one another and each form an inlet into thefurnace and/or the calciner. For example, the inert gas inlet is formedas an annular inlet around the fuel inlet. The conduit for conductingthe fuel and the inert gas is formed, for example, as a double pipe,preferably as concentric pipes with different diameters. Preferably, theinert gas is conducted directly in the vicinity of the fuel inlet or thefuel charging apparatus. This enables an economical supply of the costlyinert gas.

According to a further embodiment, the fuel inlet and the inert gasinlet together form an inlet. The fuel and the inert gas are preferablyeach fed to the calciner or the furnace in a common line. This isconstructively less complex and thus more cost-effective.

According to a further embodiment, the calciner and/or the furnacehave/has a respective plurality of inert gas inlets, in particular foradmitting different inert gases. R is also conceivable that the calcinerhas a plurality of fuel charging apparatuses, in particular two or threefuel charging apparatuses, each of which is assigned an inert gas inlet.The fuel charging apparatuses are preferably arranged at a distance fromone another along the length and/or width of the riser. For example, thefuel charging apparatuses are arranged offset from one another at anangle of 0°, preferably 60° to 270° across the cross section of theriser of the calciner. Different types of fuel charging apparatuses canbe combined with each other and also arranged differently.

According to a further embodiment, the calciner has at least one rawmeal inlet for admitting raw meal into the calciner, said raw meal inletbeing arranged upstream of the fuel inlet and the inert gas inlet in thedirection of flow of the gas within the calciner. For example, the rawmeal inlet is located between two fuel charging apparatuses or fuelinlets in the calciner. Preferably, at least one raw meal inlet isarranged upstream of the fuel inlet in the direction of flow. Thisprevents overheating of the raw meal. The combustion zone created by thecalciner firing can deliver the heat directly to the particles of theraw meal. The inert gas preferably additionally serves as a temperaturesink and also prevents spontaneous ignition of the introduced fueldirectly at the burner or burner lance mouth or at the inlet of the fuelcharging apparatus.

According to a further embodiment, the calciner has at least one,preferably two or more raw meal inlets for admitting raw meal into thecalciner and wherein at least one of the raw meal inlets and preferablyat least one fuel inlet is arranged upstream of the fuel inlet, inparticular upstream of the fuel charging apparatus, in the direction offlow of the gas within the calciner riser. Preferably, at least one orall of the raw meal inlets is arranged upstream of one or all of thefuel inlets. For example, the raw meal inlet is arranged at a distancefrom the fuel charging apparatus in the calciner.

According to a further embodiment, the cement production plant comprisesa control device which is connected to a temperature measuring devicewithin the calciner and which is configured in such a way that itcontrols/regulates the quantity of raw meal, inert gas and/or fuel inthe calciner in dependence on the temperature ascertained by thetemperature measuring device. The temperature measuring device ispreferably connected to the control device in such a way that ittransmits the ascertained temperature to the control device. Thetemperature measuring device is arranged, for example, downstream of oneof the fuel charging apparatuses. The calciner has, for example, aplurality of temperature measuring devices, each of which is connectedto the control device for transmitting the ascertained temperature. Forexample, a temperature measuring device is connected downstream of eachfuel charging apparatus. It is also conceivable that a plurality oftemperature measuring devices are arranged within the riser of thecalciner, preferably evenly distributed.

For example, the quantity of fuel in the individual fuel chargingapparatuses is controlled depending on the temperature. This ensureseven and controlled combustion within the calciner with a homogenizedtemperature distribution and avoids temperature peaks that can damagethe calciner or cause the material to melt.

The control device is designed, for example, in such a way that itcompares the ascertained temperature with a predetermined setpoint valueand, if the ascertained temperature deviates from the setpoint value, itcontrols the quantity of fuel, the quantity of inert gas and/or thequantity of raw meal in the calciner. If the ascertained temperatureexceeds the predetermined setpoint, for example, the control device isdesigned in such a way that it reduces the fuel quantity, increases theraw meal quantity and/or increases the inert gas quantity. If theascertained temperature falls below the predetermined setpoint, forexample, the control device is designed in such a way that it increasesthe fuel quantity, reduces the raw meal quantity and/or reduces theinert gas quantity.

According to a further embodiment, at least one cross-sectionalconstriction of the calciner cross section is configured within thecalciner. For example, the calciner has a plurality of cross-sectionalconstrictions in the riser. This accelerates the flow within the riserand then slows it down, so that flow-calmed regions are preferablyformed.

According to a further embodiment, at least one guide element forguiding the gas flow is arranged within the calciner. This preferablyachieves better mixing of the gas with the raw meal. This function is ofparticular importance for process control with high oxygen and lownitrogen contents in that the reduced gas quantity in the calciner dueto the lack of nitrogen content results in a higher loading after thematerial has been fed in than in systems operated with air as theoxidant. It is therefore advantageous for the load-bearing capacity ofthe particles if the material is distributed evenly over the crosssection of the riser of the calciner, Sinking of the meal into a deeperdownstream zone of the calciner riser is prevented. The guide element isdesigned, for example, as a plate, a box, a cone and/or a pyramid.Preferably, a plurality of guide elements are arranged within the riser,for example evenly spaced apart. The guide elements are made of ceramicor a ceramic fibre composite material, for example. The guide elementsare arranged in particular within the riser and/or in the fuel chargingapparatus. Preferably, a guide element is arranged at the outlet of thefuel charging apparatus into the riser, so that the inlet of fuel intothe riser is guided by means of the guide element. Preferably, the guideelement extends from the fuel charging apparatus into the riser, Forexample, the guide element is formed and arranged to guide the fuel atan angle to the inner wall of the riser. For example, the guide elementforms a diffuser with a widening cross section relative to the fuelcharging apparatus.

According to a further embodiment, the calciner has a plurality of fuelcharging apparatuses which each comprise a fuel inlet and an inert gasinlet, and wherein a guide element is assigned to each fuel chargingapparatus. The respective fuel charging apparatus is arranged, forexample, at the same height level as the guide element or is connecteddirectly upstream or downstream of the guide element. This allows anoptimized distribution of the raw meal and the inert gas within theriser, in particular in the region of the fuel charging apparatus.

According to a further embodiment, a combustion chamber is arrangedbetween the furnace and the calciner or only in the calciner, saidcombustion chamber having a meal inlet, a fuel inlet, for example a fuelcharging apparatus, and an inert gas inlet. The combustion chamber has,for example, a round cross section or is cyclone-shaped. It is alsoconceivable that the combustion chamber is designed as a calcinerreaction chamber for simultaneous calcination, so that two calciners areconnected in series or in parallel. This provides for regulation of thefuel conversion and calcination within the calciner or calciners.

The invention also comprises a method for producing cement clinker,comprising the following steps:

-   -   preheating raw meal in a preheater,    -   calcining the preheated raw meal in a calciner,    -   firing the preheated and calcined raw meal in a furnace with a        furnace burner to form cement clinker, wherein a combustion gas        with an oxygen content of 30% to 100% is supplied to the        furnace, and 1vcooling the cement clinker in a cooler, wherein a        fuel is supplied to the furnace and to the calciner.

An inert gas is supplied to each of the furnace and the calciner.

The above-described embodiments and advantages of the cement productionplant also apply to the method for producing cement clinker.

According to a further embodiment, the inert gas is supplied to thecalciner and/or to the furnace together with or separately from the fueland/or the raw meal. For example, at least two different inert gases areintroduced into the calciner and/or the furnace.

According to a further embodiment, the raw meal is admitted into thecalciner in the direction of flow of the gas within the calciner priorto the fuel and the inert gas. For example, at least part of the rawmeal and the fuel is admitted into the calciner in the direction of flowof the gas within the calciner upstream of a fuel charging apparatus.Preferably, the raw meal has a temperature of 700 C to 900° C. whenadmitted into the calciner.

According to a further embodiment, the temperature within the calcineris ascertained and the quantity of raw meal, inert gas and/or fuel thatis supplied to the calciner is controlled/regulated in dependence on theascertained temperature.

According to a further embodiment, a flow-calmed region is configuredwithin the calciner by means of at least one guide element or at leastone cross-sectional constriction of the calciner cross section.

Description of the drawings

The invention is explained in more detail below by means of severalexemplary embodiments with reference to the accompanying figures.

FIG. 1 shows a schematic representation of a cement production plantwith a calciner and a furnace according to an exemplary embodiment.

FIG. 2 shows a schematic representation of a calciner with an inert gasinlet according to a further exemplary embodiment.

FIG. 3 shows a schematic representation of a calciner with an inert gasinlet according to a further exemplary embodiment.

FIG. 4 shows a schematic representation of a calciner with a guideelement according to two further exemplary embodiments.

FIG. 1 shows a cement production plant 10 with a single-line preheater12 for preheating raw meal, a calciner 14 for calcining the raw meal, afurnace 16, in particular a rotary furnace for firing the raw meal toform clinker, and a cooler 18 for cooling the clinker fired in thefurnace 16.

The preheater 12 comprises a plurality of cyclones 20 for separating theraw meal from the raw meal gas flow. By way of example, the preheater 12has five cyclones 20 arranged in four cyclone stages one below theother. The preheater 12 has a material inlet, not shown, for admittingraw meal into the uppermost cyclone stage of the preheater 12 comprisingtwo cyclones 20. The raw meal successively flows through the cyclones 20of the cyclone stages in counterflow to the furnace and/or calcinerexhaust gas and is thereby heated. The calciner 14 is arranged betweenthe last and the penultimate cyclone stage. The calciner 14 has a riser,in particular a riser pipe, with at least one calciner firing forheating the raw meal, so that calcination of the raw meal takes place inthe calciner 14. Furthermore, the calciner 14 comprises a fuel inlet foradmitting fuel and an inert gas inlet for admitting an inert gas intothe riser. The calciner 14 further comprises a combustion gas inlet 26for admitting oxygen-containing combustion gas into the riser of thecalciner 14. The combustion gas is in particular the furnace exhaust gasenriched with oxygen. The oxygen content of the combustion gas is atmost 85% between the furnace 16 and the calciner 14. The calcinerexhaust gas is introduced into the preheater 12, preferably into thepenultimate cyclone stage, and leaves the preheater 12 downstream of theuppermost cyclone stage as preheater exhaust gas 22.

The furnace 16 is connected downstream of the preheater 12 in thedirection of flow of the raw meal, so that the raw meal preheated in thepreheater 12 and calcined in the calciner 14 flows into the furnace 16.The material inlet/gas outlet 25 of the furnace 16 is directly connectedto the riser of the calciner 14, so that the furnace exhaust gas flowsinto the calciner 14 and then into the preheater 12. The furnace 16 is,by way of example, a rotary furnace with a rotary tube rotatable aboutits longitudinal axis and arranged at a slight downward angle. Thefurnace 12 has a furnace burner 28 and an assigned fuel inlet 30 at thematerial outlet end within the rotary furnace tube. The material outletof the furnace 16 is located at the opposite end of the rotary tube fromthe material inlet 25, such that the raw meal is conveyed within therotary tube by rotation of the rotary tube towards the furnace burner 28and the material outlet. The raw meal is fired within the furnace 16 toform cement clinker. The sintering zone 32 comprises the rear region ofthe rotary tube on the material outlet side, preferably the rear thirdin the direction of material flow.

The cooler 18 for cooling the clinker is connected to the materialoutlet of the furnace 16. The cooler 18 has a cooling gas chamber 34 inwhich the clinker is cooled by a cooling gas flow. The clinker isconveyed in a direction of conveyance F through the cooling gas chamber34. The cooling gas chamber 34 has a first cooling gas chamber portion36 and a second cooling gas chamber portion 38, which adjoins the firstcooling gas chamber portion 36 in the direction of conveyance F. Thefurnace 16 is connected to the cooler 18 via the material outlet of thefurnace 16, so that the clinker fired in the rotary furnace 20 fallsinto the cooler 18.

The first cooling gas chamber portion 36 is arranged below the materialoutlet of the furnace 16, so that the clinker from the furnace 16 fallsinto the first cooling gas chamber portion 36. The first cooling gaschamber portion 36 constitutes an inflow region of the cooler 18 andpreferably comprises a static grate 40 which receives the clinkerexiting the furnace 16. In particular, the static grate 40 is completelyarranged in the first cooling gas chamber portion 36 of the cooler 10.Preferably, the clinker from the furnace 16 falls directly onto thestatic grate 40. The static grate 40 preferably extends completely at anangle of 10° to 35°, preferably 14° to 33°, in particular 21 ° to 25° tothe horizontal, so that the clinker slides along the static grate 40 inthe direction of conveyance.

The first cooling gas chamber portion 36 is adjoined by the secondcooling gas chamber portion 38 of the cooler 18. In the first coolinggas chamber portion 36 of the cooler 18, the clinker is cooled inparticular to a temperature of less than 1000° C., wherein the coolingis performed in such a way that a complete solidification of liquidphases present in the clinker into solid phases takes place. Whenleaving the first cooling gas chamber portion 36 of the cooler 18, theclinker is preferably completely in the solid phase and at a temperatureof 1000° C. or less. In the second cooling gas chamber portion 38 of thecooler 18, the clinker is further cooled, preferably to a temperature ofless than 100° C. Preferably, the second cooling gas flow can be dividedinto a plurality of partial gas flows which have different temperatures.

The static grate of the first cooling gas chamber portion 36 has, forexample, passages through which a cooling gas enters the cooler 18 andthe clinker. The cooling gas is generated, for example, by at least onefan, blower or pressure vessel arranged below the static grate 40, sothat a first cooling gas flow 42 flows from below through the staticgrate into the first cooling gas chamber portion 36. The first coolinggas flow 42 is, for example, pure oxygen or a gas containing 15 vol % orless of nitrogen and 30 vol % or more of oxygen. The first cooling gasflow 42 flows through the clinker and then flows into the furnace 16.The first cooling gas flow forms, for example, part or all of thecombustion gas of the furnace 16. The high proportion of oxygen in thecombustion gas results in a preheater exhaust gas consistingsubstantially of CO2 and water vapour, and has the advantage ofeliminating the need for costly downstream purification processes forexhaust gas purification. Furthermore, a reduction of the process gasquantities is achieved, so that the plant can be dimensionedconsiderably smaller.

Inside the cooler 18, the clinker to be cooled is moved in the directionof conveyance F. The second cooling gas chamber portion 38 preferablyhas a dynamic, in particular movable, grate 44, which adjoins the staticgrate 40 in the direction of conveyance F. Below the dynamic grate 44, aplurality of fans are arranged by way of example, by means of which thesecond cooling gas flow 46 is blown from below through the dynamic grate44. The second cooling gas flow 46 is, for example, air.

In FIG. 1 , a comminution device 48 is connected to the dynamic grate 44of the second cooling gas chamber portion 38 by way of example. Afurther dynamic grate 50 is connected to the comminution device 48 belowthe comminution device 48. Preferably, the cold clinker 52 has atemperature of 100° C. or less when leaving the cooler 18.

For example, cooler exhaust air 54 is discharged from the second coolinggas chamber portion 38 and fed into a separator 56, such as a cyclone,for separating solids. The solids are fed back to the cooler 18, forexample. An air-to-air heat exchanger 58 is connected downstream of theseparator 56, so that the cooler exhaust air preheats air within theheat exchanger 58, which is fed to a raw mill, for example.

FIG. 2 shows a detail of a cement production plant 10 according to FIG.1 , wherein the regions not shown correspond, for example, to those ofFIG. 1 and like reference signs represent like elements. The calciner 14shown in FIG. 2 has two fuel charging apparatuses 60 by way of example.R is also conceivable that the calciner 14 has only exactly one fuelcharging apparatus 60 or more than two fuel charging apparatuses 60. Thetwo fuel charging apparatuses 60 are mounted at a distance from eachother on the riser 62 of the calciner 14. By way of example, the fueldelivery devices 60 are mounted at different height levels on the riser62. Each fuel charging apparatus 60 is assigned a fuel inlet 24 and aninert gas inlet 64, such that fuel and inert gas are directed into thefuel charging apparatus 60. The fuel charging apparatuses 60 arearranged offset from each other by 180°, by way of example. For example,the fuel charging apparatus comprises a means for transporting the fuel,such as a screw conveyor or a chute. The fuel or fuels can also be fedin pneumatically, for example, by conveying with the aid of an inertgas.

FIG. 2 further shows that a fuel inlet 30 and an inert gas inlet 68 areassigned to the furnace burner 28 so that fuel and inert gas aresupplied to the furnace burner 28. The fuel inlet 24, 30 and the inertgas inlet 64, 68 are formed, for example, separately from each other oras a common inlet into the calciner 14 or the furnace 16. The inert gasis, for example, CO2 or water vapour. The inert gas may serve both as aconveying agent and to influence the ignition or control of thecombustion process,

In FIG. 2 , the raw meal inlet 70 in the calciner 14 is formed by way ofexample by the solids outlet of the penultimate cyclone stage. The rawmeal inlet 70 is arranged, for example, between the two calciner burners60. Alternatively, the raw meal can preferably be fed below each of theindividual combustion zones downstream of the fuel inlets 30. Anotherpossibility for feeding raw meal and fuel is to use a combustion chamberarranged parallel to the riser of the calciner to feed fuel and mealsimultaneously in a low-oxygen zone. Preferably, the fuel is fedcentrally into a downwardly directed combustion chamber. Around the fuelfeed, the raw meal is fed on a radial circumference or on thecircumference of the cylindrical combustion chamber in such a way thatthe fuel is surrounded by a curtain of meal. At the lower end of thecombustion chamber, this connects to the upwardly directed riser of thecalciner. The fuel encased by the meal is introduced into theoxygen-rich calciner flow, where it is ignited. The heat is directlyconsumed by the calcining reaction of the raw meal.

The calciner 14 has, by way of example, a temperature measuring device66 for ascertaining the temperature inside the calciner 14. The cementplant 10 further comprises a control device 72 which is connected to thetemperature measuring device in such a way that the temperaturemeasuring device 66 transmits the ascertained temperature to the controldevice 72. The control device 72 is connected to the fuel inlet 24, theraw meal inlet 70 and/or the inert gas inlet 64 and is designed in sucha way that it controls/regulates the quantity of fuel, raw meal and/orinert gas in the calciner 14 in dependence on the ascertainedtemperature.

FIG. 3 shows a further example of a calciner 14 of FIGS. 1 and 2 ,wherein like reference signs represent like elements. The riser 62 ofthe calciner 14 has a plurality of different cross-sectional areas. Thefuel charging apparatuses 60 of the calciner 14 are attached to the sameside of the riser 62, for example without angular offset, but atdifferent height levels. In the direction of flow of the gas within theriser 62, each fuel charging apparatus 60 has a respective raw mealinlet 70 directly upstream and/or downstream. The fuel inlet 24 and theinert gas inlet 64 are each arranged at the fuel charging apparatus 60of the calciner 14, in particular at the same level as the respectivefuel charging apparatus 60.

The cross-sectional constrictions ensure balanced mixing within theriser and thus lead to even combustion and temperature distribution inthe longitudinal and transverse directions of the riser of the calciner.

In FIG. 4 is a detail of a calciner 14, wherein like reference signsrepresent like elements. The calciner 14 has a guide element 73, whichin the left-hand illustration is attached by way of example within theriser 62 and in the right-hand illustration is attached by way ofexample to the fuel charging apparatus 60 in the specific form of aflue.

In the left-hand illustration, the guide element 73 is arranged in sucha way that it causes a constriction of the cross section of the riser62. The guide element 73 is in particular in plate form, chamber form orbox form and is attached to the inner wall of the riser 62, moreover, byway of example, at the same height and opposite the fuel chargingapparatus 60.

In the right-hand illustration, the guide element 73 has the exemplaryform of a diffuser, wherein the cross section of the guide element 73increases in the direction of flow of the fuel. The guide element 73 isattached to the fuel charging apparatus 60, in particular at the mouthof the fuel charging apparatus 60 into the riser 62, and in particularallows a targeted introduction of the fuel into the riser 62. It is alsoconceivable that the guide element 73 is flush with the riser and doesnot project into it, so that a uniform inlet of the fuel into the riser62 is allowed.

The guide element 73 is formed, for example, from ahigh-temperature-resistant ceramic or a fibre composite material.

LIST OF REFERENCE SIGNS

10 cement production plant

12 preheater

14 calciner

16 furnace

18 cooler

20 cyclone

22 preheater exhaust gas

24 fuel inlet of the calciner

25 material inlet into the furnace

26 combustion gas inlet of the calciner

28 burner or burner lance of the furnace

30 fuel inlet of the furnace

32 sintering zone

34 cooling gas chamber

36 first cooling gas chamber portion

38 second cooling gas chamber portion

40 static grate

42 first cooling gas flow

44 dynamic grate

46 second cooling gas flow

48 comminution device

50 dynamic grate 50

52 cold clinker

54 cooler exhaust air

56 separator

58 heat exchanger

60 fuel charging apparatus

62 riser of the calciner

66 temperature measuring device

64 inert gas inlet

68 inert gas inlet into the furnace

70 raw meal inlet into the calciner

72 control device

73 guide element

1.-16. (canceled)
 17. A cement production plant comprising: a preheaterconfigured to preheat raw meal; a calciner configured to calcine the rawmeal that has been preheated; a furnace with a furnace burner configuredto fire the raw meal to form cement clinker, wherein the furnace has acombustion gas inlet configured to admit a combustion gas with an oxygencontent of 30% to 100% into the furnace; and a cooler configured to coolthe cement clinker; wherein the calciner and the furnace have arespective fuel inlet configured to admit fuel into the calciner and thefurnace, wherein the calciner and the furnace have a respective inertgas inlet for respectively admitting inert gas into the calciner and thefurnace.
 18. The cement production plant of claim 17 wherein the fuelinlet and the inert gas inlet are arranged separately from one anotherand each forms an inlet.
 19. The cement production plant of claim 17wherein the fuel inlet and the inert gas inlet together form an inlet.20. The cement production plant of claim 17 wherein at least one of thecalciner or the furnace has multiple inert gas inlets.
 21. The cementproduction plant of claim 17 wherein the calciner has a raw meal inletconfigured to admit raw meal into the calciner, wherein the raw mealinlet is arranged upstream of the fuel inlet and the inert gas inlet ina direction of flow of gas within the calciner.
 22. The cementproduction plant of claim 17 wherein the calciner has a raw meal inletconfigured to admit raw meal into the calciner, wherein the raw mealinlet is arranged downstream of the fuel inlet and the inert gas inletin a direction of flow of gas within the calciner.
 23. The cementproduction plant of claim 17 wherein the calciner has at least two rawmeal inlets configured to admit raw meal into the calciner, wherein atleast one of the at least two raw meal inlets is arranged upstream ofthe fuel inlet in a direction of flow of gas within the calciner. 24.The cement production plant of claim 17 comprising a control device thatis connected to a temperature measuring device within the calciner andthat is configured to regulate a quantity of at least one of raw meal,inert gas, or fuel in the calciner based on a temperature ascertained bythe temperature measuring device.
 25. The cement production plant ofclaim 17 wherein at least one cross-sectional constriction of a calcinercross section is configured within the calciner.
 26. The cementproduction plant of claim 17 comprising a guide element for guiding atleast one of gas flow or fuel within the calciner.
 27. The cementproduction plant of claim 27 comprising multiple of the guide element,wherein the calciner includes fuel charging apparatuses that eachcomprises a fuel inlet and an inert gas inlet, wherein one of the guideelements is assigned to each fuel charging apparatus.
 28. The cementproduction plant of claim 17 comprising a combustion chamber disposedbetween the furnace and the calciner, the combustion chamber having araw material inlet, a fuel inlet, and an inert gas inlet.
 29. A methodfor producing cement clinker, the method comprising: preheating raw mealin a preheater; calcining in a calciner the raw meal that has beenpreheated; firing in a furnace with a furnace burner the raw meal thathas been preheated and calcined to form cement clinker, wherein acombustion gas with an oxygen content of 30% to 100% is supplied to thefurnace; and cooling the cement clinker in a cooler; and supplying afuel and an inert gas to the furnace and to the calciner.
 30. The methodof claim 29 comprising supplying the inert gas to the calciner and/or tothe furnace together with the fuel.
 31. The method of claim 29comprising supplying the inert gas to the calciner and/or to the furnaceseparately from the fuel.
 32. The method of claim 29 comprisingadmitting the raw meal into the calciner in a direction of flow of gaswithin the calciner prior to the fuel and the inert gas.
 33. The methodof claim 29 comprising: ascertaining a temperature within the calciner;and regulating a quantity of at least one of raw meal, inert gas, orfuel that is supplied to the calciner based on the temperature.
 34. Themethod of claim 29 wherein a flow-calmed region is configured within thecalciner by way of a guide element or a cross-sectional constriction ofa cross section of the calciner.